How Far Away Is Lightning?

Next time you're stuck in a thunderstorm, try this easy way to calculate how far away you are from lightning strikes.

Transcript

00:00 How far away is lightning? Picture it. You're stuck in a thunderstorm and you

00:06 need to figure out how long you have to take cover. The last thing you want to do

00:10 is math, but here's an easy way to calculate how far away you are from

00:14 lightning strikes. When you see a flash of lightning, count the number of seconds

00:19 that pass between that flash and the crack of thunder that follows it. Got

00:25 that number? Now, divide it by five. The resulting number will tell you how many

00:31 miles away you are from where the lightning just struck. So let's say you see a

00:35 jagged burst of light and it takes five seconds before you hear the boom. That

00:41 means the lightning struck one mile away from you. A 10-second gap means the

00:46 lightning is two miles away. This math could keep you safe. The National

00:51 Weather Service recommends that you take cover if that time between the flash and

00:56 the boom is 30 seconds, which means the lightning is six miles away. There's

01:02 science behind that calculation, but it's a little complicated. Light travels

01:08 186,291 miles per second, while sound travels just 1,088 feet per second,

01:15 depending on air temperature. The gist is that light travels much quicker than

01:20 sound, so you see the light from the lightning basically in real time. The

01:26 sound from the thunder, however, travels much slower. That's why you can get a

01:30 distance by knowing how long it took the sound from the thunder to reach your

01:34 ears. How far away is lightning? Just another one of life's little mysteries.